Bulb



FIG. 1 is a top, front and right side perspective view of a bulb showing my new design;

FIG. 2 is front elevational view thereof;

FIG. 3 is a right side elevational view thereof, the left side being a mirror image;

FIG. 4 is a top plan view thereof; and,

FIG. 5 is a bottom plan view thereof. 

The ornamental design for a bulb, as shown and described. 